Selective amplifying apparatus



A Apr. 24, H923.

l. PUPIN v SELECTIVE AMPLIFYING APPARATUS original Filed not; 1 '0 1918 40 "0 ,J0 4a J0 60 70 60 so k3 Sheets-Sheet. l

Ar. 24, H923. 1,452,933

A M. l. PUFIVN SELECTIVE AMPLIFYING APPARATUS Original Filed Ocfc. l0 1918 I5 Sheets-Sheet 2 @AML I @QM Apr. 24', i923.-

s Smeets-sheet 5 Original Filed Oct. l0 1918' @aient pr. 24, 1923.

l`1,452,93 f i carica.

:MIC I DVORSKY PUPIN, OF NORFOLK, CNNECTICUT, ASSGNOR T HOUSE ELECTRIC AN'D MANUFACTURING COMPANY, 0Fv EAST PITTSBURGE,

A CORPORATION OF PENNSYLV 4 i snnncrzwn'4 AMPLrrYrNe arraaa'rns.

Application filed October 10, 1918, Serial No. 257,571. Renewed September 14,' 1922. erial No. 588,287.

To all 'whom 'it may concern.: Be it known that I, MICHAEL I. PUrIN, a citizen of the United States, residing at Norfolk, in the county of Litchield, and 5 State of Connecticut, have invented certain new and useful Improvements in Selective Amplifyin Apparatus; and I do hereby declare the ollowing to be a full, clear, and exact description of the.invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to selective amplifying apparatus for electric energy waves, and has for its general object the provision of an improved apparatus of this character. A more particular object of the invention is the provision of a selective multi-step vacuum tube amplifier. @ther objects of the invention Will be brought out. in th'e courseof the following description. ln the art of Wireless telegraphy and telephony of today, selectivity with respect to the frequency of the signalling harmonic electromotive forces isobtained by balancing indu/etance reactions againsty capacity reactions, and ahigh degree of selectivity is obtained by the employment of conductors of relatively low resistance reactions, and large time constants. Selectivity obtained in this manner produces a.system of electrical conductors in which the natural oscillations are undamped, so that disturbing electrical pulses following each other at rapid intervals maintain in such a systein oii electrical conductors amore or less continu- 'ous train of oscillations ofthe vsame periods as those for which the conductors Vare selective. The disturbances arising from these oscillations are just as' objectionable as the disturbances that would be produced by the pulses directly.- .Hence, thisskind of selectivityis no protection against disturbances due to pulse excitation. lhile the present invention makes use of the balancing of inductance reactions by capacity react-ions, it does not depend upon this balancing for the high degree of selectivity and instead of employing electrical conductors of relatively small resistance reactions and large time constants, the dissipative reactions. are made as large as practicable, and the time vconstants are as'small as practicable, so that the natural oscillations, when they exist at all,

are `very highly damped, so highly indeed, that theyare incapable of producing, by interference beats, the Well known heterodyne low frequency, and for this reason, as will be shown presently, the selectivity described yhere will protect from disturbing interfer-v ences due to pulse excitation' just as Well as it docs with respect to steady harmonic elec- ,tromotive forces.-

rl`he selective amplifying apparatus of the present invention is made selective with respect to the impressed (s'gnalling) frequency by the action of a deice for balancing in phase and amplitude alternating or pulsating electromotive 'force waves. A suitable devlce for this purpose is described inmy copen'ding application Serial `No. 257,570, filed October 10, 1918, and I shall throughout this speci'cation, as in the copending, case, designate the device as a Wave balance.l

ln its broad aspect, the invention involves the provision of a circuit of high dissipative impedance and an amplifying device excited by an electrical reaction of. the circuit, together with means for impressing on the circuit a negative resistance reaction whereby power is conveyed to the circuit from a source independent thereof and the exciting electrical reaction is increased. The negative resistance'. reaction is, in accordance with the invention,-obtairi,ed fron. a negative resistance compensator/of such a character that the desired selective action of the apparatus is due to the electrical reactions thereof. The Wave balance of my aforementioned application `is admirably adapted for use as such a negative resistance compensator. In the preferred formof the invention, the wave'balanc'e is electrically, associated with a vacuum tube amplifier andA a high resistance conductor, the resistance load,- so arranged that the exciting electromotiveforce for the grid ofthe amplifier is dependent upon the voltage drop or resistance reaction of the resistance load, and this reaction is augmented by arranging the Wave conductor so that atfthe signalling frequency the E. M. F. induced in its secondaries acts, in part, as a negative resistance reaction. I prefer toemploy a multi-step apparatus containing several sin le steps and in which each step has a mo erate selectivity which is then transformed in geometrical progression into high selectivity by the cooperation of the several steps acting in cascade.` In such an apparatus, each step includes `a circuit of 4high dissipative 5 impedance and an amplifying device excited by an electrical reaction of the circuit together with a negative resistance compensator Which by conveying power to the circuitY v from a. source independent thereof increases the exciting electrical reaction. Such a form of the invention is ofparticular advantage in super-audible or high frequency sound signalling systems utilizing compressional Waves propagated through suitable media. This type of signalling system will be referred to hereinafter as supersonic signalling, and -in this connection another aim Aof the invention is the provision of an improved signalling system by supersonics.

In the accompanying drawings, which form a part of this specification, Fig. 1 represents, diagrammatically, a single step vacuum tube amplifier embodying the principles of the present invention; Figs. 2 and 3 are explanatory curves which will be explained in' detail hereinafter; Fig. 4 represents,. diagrammatically, a multi-step vacuum tube amplifier embodying the iiivention; Figs. 5 and 7 diagrammatically 0 represent modified arrangements embodying the principlesl ofthe invention; and Fig. l6 represents, diagrammatically, a supersonic signalling system embodying the invention.

Referring' to Fig. 1 of the drawings, there isv diagrammatically represented a low impedance vacuum tubehaving a grid. 10, a heating flaiiient 11, and a plate 12. A local source of`direct current energy, such, for 40 example, as the battery 13, serves to supplyl the relatively low voltage` say about seven volts, for maintaining a filament cur- .Ient of about 1.75'amperes, and the relartively high voltage, say about 110 volts, 5 `for the wing or electron current between the filament 11 and the plate 12. 's

A conductor lt of high resistance.l say Y about 16,000 ohms, made up of high resistance material and given a form possess- Aing as small capacity as possible, is included in series relation with the source of electromotive force to beamplified, and is connected to the grounded terminal of the lament 11. Included in series relation with the high resistance conductor 14 are the two.

secon ary coils 15 and 16 of a wave balanceof the form described in my aforementioned application. This Wave balance comprises inner and outer laminated layers of tin foil 18 and 18 between which is positioned the coiled wave conductor 17, separated by suitable dielectric layers from each tin foil layer. The wave conductor .hasvsubstantlally `uniformly distributed in- 5 ductanoe and-capacity and possesses suf ficiently high resistance and capacity to make it a true'wave conductor and to render it practically aperiodic. The secondary coils 15 and 16 kare inductively associated with the Wave conductor 17 and are rela-v tively niovable with respect to each other` and to the wave yriductor. The foregoing elements of the wave balance are diagram-- matically indicated in Fig. 1 of the drawings, while in the other figures of the drawings the wave conductor and tin foil layers are symbolically represented by reference numerals 17 and 18, respectively.

A condenser 19 of suitable and variable capacity is included iii series with the secondary coils 15 and 16. I have found that the secondary coils' 15 and 16 may advan'- tageously'have about five hundred 'turns of No. 39 copper wire wound in six layers which are separated by several thicknessesof pai'affiiied paper in order to reduce their mutual capacity. The distance between these layers and the outer tinfoil layer should be as large as practicable, so as to diminish the capacity to ground of the layers.

The plate 12 is connected to the positive terminal of the battery 13 through a suitable inductance coil 20 having an inductancc of about .04 henries at 50,000` P. P. S., its winding and magnetic circuit being so constructed as to avoid capacityasmuch as y I practicable. One terminal of the wave conductor 17 is connected to plate `12`through a blocking condenser 21 designed to prevent the' direct current voltage of plate 12 from establishing a direct current through the wave conductor. The other terminal of the wave conductor 17 is' grounded through the common ground connection 22.

The characteristic elements of theI arrangement just described are:

First-The secondary coils or circuits 15 and 16 ofthe Wave balance are placed at approximately half a wave lengthfromjv each other for the frequency of the impressed (signalling) electromotive force, that is, the frequency which is to be transmitted over them in the direction indicated 'bythe arrow, and they are connected inl the reverse order. That is to say, if a ,direct current is sent through Athem and develops in coil 15 a plus pole on the left and a minus pole on the right, then this current Vwill develop in the coil 16 a minus pole on the left and a plus pole on the right. Hence, an alternating current of the signalling frequency flowing through the- Wave conductor 17 will develop in coils 15 and 16 electromotive forces in the same direction. since these two coils are positioned approxil mately one-half a wave length apart. For lower frequencies, for which the wave length rs longer, the electromotive forces developed in the two secondary coils will be opposing each other. This inverse series connection H. Armstrong and myself, Serial No. 51,151,

Cil

of .the two secondary coils of the wave balance an important feature of this invcn.

including the secondary coils and the highv resistance conductor 14 from the directcure rent battery 13 which maintains the electron current. The meaning andv character of this negative resistance reaction is explained and discussed in my co-pending application Serial No. 51,150, filed September 17. 1915, and in a co-pending application of Edwin filed September 17, 1915. To produce this negative Aresistance reaction of suitable amount, the terminals of the secondary coils 15 and 16 are properly connected into -the circuit and the relative positions ofthe coils properly adjusted. In this operation, one must be guided by a VVheatstone bridge. The negative resistance reaction acts against the positive resistance reaction of conductor 14 which has a high resistance, and in this mannertheeffective resistance'of the conductor is diminished. To this diminution is due, in part, the selectivity of the conductor just mentioned.

TfZ1'cZ.-When at the signalling frequency, one component of the electromotive force induced in the secondary coils 15 and v16 acts as a negative resistance reaction of suitable magnitude. then the other component of thisv induced clectromotive force will appear, generally, as a capacity reactionwhich will reduce the inductance reaction of the secondary coils. rl`he remainder o-f the inductance reaction is reduced further bythe capacity of the variable condenser 19 or, if that remainder is a. capacity reaction, then an inductance reaction is introduced into the circuit by substituting in place of the variable condenser 19 a suitable variable inductance.

1t is desirable', but not absolutely necessary,`

that for the signalling frequency the only effective reaction in the circuit19--15-16-- in the ing impedance of the samey circuit.

the larger current which is established by a given alternating electromotivey force between the source of this electromotive force and ground, the larger will be the resistance reaction of the conductor 14, and the larger will be the excitation of the grid 10, and hence the larger will be the amplifying power of the vacuum tube; that is tosay, the larger will be the ratio between the alternatiug potential at the plate 12 and the vfundamental alternating potential impressed on the condenser 1S). But the current in the circuit 19-15-16-14-22 corresponding to a given alternating'potential impressed on the condenser 19 dependson the impedance,

only, of this circuit. Hence every operation employed here to lower this impedance will increase the amplifying power of the arrangement represented in Fig. 1.

In Fig. 2 of the drawings, there is shown a curve in which the abscissae represent the frequency in kilo-cycles of the alternating electromotive force impressed upon the circuit 19-15 multiplied by 10:I represent the correspgxlld- 1.6#14-22 and the ordinates curve was plotted from the following Itable inv which the first column, designated f,

vgives the frequency in kilo-cycles of the impressed voltage. lVhile the columns, designated R, XL, XC, 1, give the corresponding resistances, inductance. reactances, capacity reactances and impedances, respectively, of the circuit. The data given in this table were obtained experimentally by a high frequency lVheatstonebridge.

From the curve of F ig. 2, it will he observed that the circuit 19--15-16-14-22 behaves similarly to a tuned circuit of largeselectivity, although it has a high effective resistance and a small time constant. 1n the case specifically described. herein, the natural re slstance of the conductor 14. is very large, 16,000 ohms, and it is diminished at the critical frequency by the combined action of the vacuum tube and the wave balance to 1300 ohms, the effective inductance being ,quite small at this frequency, approximately 102 henry, so'that the time constant is small, making the natural oscillations of the conductor highly damped. Owing to the inverse series connection of the two secondary coils 15 and 16 of the Wave balance and the phase shifting of the electromotive forces induced in these coils. the eective resistance-in the circuit 19-15--16--14-22 increases rapidly, and also the capacity reaction increases, but not so rapidly, when the frequenc-y of the impressed electromotive force diminishes. When the frequency increases, thc effective resistance increases also, but not so rapidly' as the effective inductance. This is shown clearly in the curve of Fig. 2. The result is a circuit with a highly damped natural oscillation, possessing, nevertheless, a high degree of selectivity. A simple consideration will show that this result is impossible by tuning, in the usual way, an ordinary circuit having a small time constant.

in Fig. 3 of the drawings, there is shown a curve the abscissae of which represent the .frequency in kilo-cycles (K) of the impressed electromotive force and the ordinates represent the amplifying power of the single step amplifier for these frequencies. The data from which this curve was drawn were obtained experimentally by the wave balance method described in my copending application' Serial Number 257,570, aforementioned. As is to be expected, the curve of Fig. 3 is of the same character as that of Fig. 2. It will be observed that frequencies considerably above or below the critical frequency are not only not amplified by the action of the vacuum tube, but that they are actually weakened.

A multi-step amplifier having for several of its steps single step amplifiers like the one described in connection with Fig. 1 can have its selectivity increased to any desirable limit by increasing the number of these selective steps, although each' step may have a. vvery moderate selectivity. Such a multistep amplifier acts like an aperiodic pilot conductor. An aperiodic pilot conductor is characterized by the fact that it is not. capable of sustaining local oscillations, that is, the unit sections of which it is composed are not capab-le of sustaining local oscillations because they have no natural period of oscillation. The high selectivity obtained inathis way is another characteristic feature of this invention. 1t holds good not only for yharmonic electromotive forces, but also, as is well known, for pulses in the sense that a selective and highly damped multistep amplifier, as hereinafter described, will eliminate all the harmonic components of the pulse, the frequencies of which differ appreciably from the critical frequency of the multi-step amplifier, and, on account of the high damping, will not be set into violent vibrations by impulse excitation. This multi-step amplifier will now be briefly described. v Y

Referring to Fig. 4 of the drawings, t first step of the selective multi-step ampli fier therein diagrammatically represented is the same as .shown in Fig. 1, and corresponding elements of the two figures are represented by the same reference numerals. rIfhe second step comprises a vacuum tube having a filament 11', a grip 10 and a plate 12', with its associated inductance 20, corresponding to the inductance 2O in the first step. This second step is connected to the first step by a three-step pilot conductor, consisting of three equal condensers 30, 31, 32, connected in series and three shunting resist-ances 33, 34, 35. This pilot conductor and its action are fully described in my copending application Serial Number 215,293, filed February 4, 1918, and need not be further considered herein. The third stepis identical with the first step and the fourth step is identical wit-h the second step. 'it will thus be seen that the several steps of the multi-step apparatus are connected in series or cascade. As indicated in Fig. 4, the two steps, rendered selective by the action of the wave balance, are separated by al step which does not employ the wave balance. This is done for the purpose of di- .minishing the coupling between steps having a wavei balance, a procedure which is not absolutely necessary, but often desirable when great stability in the operation of thc selective multi-step amplifier is aimed at.

The inductance or impedance coil 20 should have as high resistance as prac;y ticable, which is adjusted by selecting steel plates for the iron core which have the proper thickness. This high resistance is desirable for the purpose of preventing the formation of undamped oscillatory circuits including the coil 20 and the secondary coils l5 and 16 and theircapacity to ground. Fig. 5 of the drawings diagrammatically represents an arrangement of apparatus in which a wave balance and vacuum tube amplifier are employed, in accordance with the principles of the present invention, in combination with a. step-up transformer. The specific details of this arrangement and its particular advantages are described in au application filed concurrently herewith, Serial Number 257,572. In the arrangement of.' Fig. 5, the grid 10 of the vacuum tube is excited by the secondary voltage of the stepup transformer 41-44. The primary winding 41 of the transformer is included in the circuit of high dissipative impedance including the high resistance 14, the secondary coils 15 and 16 and the adjustable condenser 19.

. One terminal of the primary and secondary windings. 41 and 44, respectively, of the transformer are connected together and to the ground connection 22. The other elements of the wave balance and vacuum tube are connected as in LFig. 4. A pilot conductor, comprising condensers 30, 31 and 32 and resistances 33, 34 and 35, and a vacuum tube 1011"'-12, serve to couple together, as in the arrangement" of Fig. 4, alternate steps including the wave balance, .so that intensa the several steps-of the multistep apparatus are thus connected in series or cascade.

It will be noted in the arrangement of Fig. 5, that the grid of the firstvacuum tube is excited by the voltage of the transformers secondary winding 44 instead of by the resistance reaction of the conductor 14. Other# wise, the function and operation of the high resistance conductor 14 is the same as in the arrangements hreinbefore described. The circuit in which the primar)7 winding 41 is included has a high dissipative impedance, but., due to the action of thewave balance, the effective impedance at the critical frequency, that is; the frequency of the impressed (signalling) electromotive force, is

greatly reduced. As in the preceding arrangements, so in the arrangement of Fig. the grid 10 of the vacuum tube is excited by an electrical `reaction of a circuit of high dissipative impedance, and the Wave balance, acting as a negative resistance compensator,

Aconveys power to this circuit from a source independent thereof, for. example the vacuum tube battery, and thereby increases the exciting electrical reaction.

. In Fig. 6 of the drawings, there is diagrammatically represented a system of receiving apparatus for supersonic signalling in Which a selective multi-step vacuum tube amplifier embodying the principles of the present invention is employed in the reception of the signals by supersonics. In this figure, a quartz oscillator 40, comprisinga quartz crystal having metallic electrodes or conducting plates operatively arranged on the surface of the crystal, or similar receiving device, employed in supersonic signalling.`

has its conducting plates connected in series with the primary winding 41 ofk a transformer and the secondarvcoils 15 and 16 of a Wave balance. A high resistance 42 and an adjustable inductance 43 are also shown in the figure as included in this series circuit. The resistance 42 corresponds to the resistance 14 and constitutes the load resistance hereinbefore described. The invreducing the capacity reaction of the oscillator 40. The secondary. Winding 44 of the transformer is connected to the grid 10 of the. vacuum tube amplifier, just as in the arrangement of Fig. 5.1 From the foregoing descriptions, it will Vbe evident that the vacuum tube and Wave balance are connected so as to suitably reduce the eiiective primary resistance of the transformer, as described and explained in my aforementioned .application Serial Number 257, 572. The first vacuum tube 10'-11-12, withA its associated pilot conductor., serves to couple the transformer step or unit ,to the selective multi-step amplifier of the tvne described in con nection with Fig. l4. The right-hand terminal of the arrangement represented in Waves, nor will 'it transmit internal disturbance due to the ordinary irregular actions of the vacuum tubes.

It should be observed that the vacuum tubes employed here are low impedence tubes, so-called power-tubes, `which are not usually employed inthe construction of 'ampliiiers. on account of their low amplification power. ln this invention, however, they are given a large load tocarry, the resistance 'load mentioned above, and under these conditions the power-tubes have a chance to do work and thus produce a highldegree of amplification. lt should also be observed that high-impedance tubes are not eicient in amplifying very high frequencies for reasons 'which are Well understood and need not be discussed here. The system described here is, believe, the first eiiicient system for amplifying very high frequencies.

There are obviously other arrangements of circuits by which energy7 can be transferred selectively7 from a local source to the exciting 'circuitA for the purpose of increasing the electrical reaction YWhich excites the amplifying or controlling device Without modifying seriously the aperiodic character of the exciting circuit, but all these arrangements are equivalent modifications of the one described herein which I now consider to be the best arrangement for carrying out in practice the fundamental principles of this invention.

v Fig. 7 of the drawings diagrammatically represents a system of receiving apparatus denser 21 of the former arrangements are,-

however. omitted in the simplified arrangement ofvFig. 7, and the wave conductor 17 is connected between the plate 12 of the vacuum tube and the positive or un-Y grounded terminal of the battery 13. The

tin foil layers 18 and 18 are not electrically connected to the wave conductor, as in the preceding arrangements, but are connected together and to the common ground connection 22. The reactances 20 are. moreover,

apparatus of Fi 7 is the same as hereinbefore describe and corresponding ele- `ments are designated by the same reference characters. The arrangement of Fig. 7 is of particular advantage in cases where it is possible to use low voltage. It will be noterl` that the Wave conductor 17 is included in the electron circuit of the vacuum tube 10-11--12, and, accordingly, the wave balance 17-18, acting as a negative resistance compensator, serves to overcome the resistance 50 by negative resistance reaction.

The selectivity obt'ained in accordance .with the principles of the present invention` rather than capacity reactance, as in ordinary tuning. This result is brought about by the high effective resistance or dissipative impedance of the circuit, which is a characteristic feature of the present invention. However, at the critical or signalling frequency, this high eective resistance 1s substantially overcome by the negative resistance reaction. By providing this higl 'effective resistance, all oscillatory circuits,

in which the occurrence of disturbing oscillat-ions aects the selectivity, are rendered substantially aperiodic, without, however, impairing the'selectivity for the critical or signalling frequency, because atV this -fre-- quency t negative resistance compensator serves to substantially wipe out or overcome the high edective resistance. L

The wave balance* with its secondary coils or circuits in `inverse series connectionlhas particular advantages as a 'negative resistance compensator in. combination with a circuit of high dissipative impedance. .As

a result lof the inverse series connection, the selectivit 1s increased, because neglecting the (1)0ssibleiesence of odd -harmonics whic would not appreciably!v affect the system, at only 'the criticalorJ-signalling frequency do the induced electromotive o of these secondary coils act in conjunction. At dall other frequencies theelectromotive i forces induced in the tvvo secondary coils are more or less in opposition. Furthermore, as a result of the phaseshifting of the electromotive fofces induced in the secondary` circuitsv at frequencies other than the critig calor signalling frequency, the inductance itself of the secondary coils is substantially eficaces actually increases as the frequency increases, thereby further increasingA the selectivity. For these reasons, I prefer to employ a Wave balance in which the secondary coils are arranged in inverse series connection, but it Will be understood by thoseskilled in the art, in View of the foregoingexplanations,

that the broad principle underlying the present invention does notl necessarily involve. this particular connection of the secondary coils, or even, in fact, the use of distinct secondary coils or circuits, since the wave balance may be in the form of an autotransformer without departing from the;

spirit of the invention. In fact, the wave 'balance -may be considered broadly as a 1. A multi-step selective amplifying apparatus comprising several units connected in cascade, each of said units including a circuit containing a high resistanceconduc tor, a control device excited by an electrical reaction of said circuit, a source of electric energy, and a negative resistance coin ensator controlled by said device and w ich by conveying pbwer to said circuit from said source increases saida exciting electrical reaction.

v 2. A multi-step selective amplifying apparatus comprising several units connected in cascade, each of Isaid units including a circuit containing a high resistance conductor, a vacuum tube excited by an electrical reaction oi said circuit, a soyrce' of electric energy, and a' negative resistance compensator controlled by said tube and which by conveying power-from-said sourcevl increases slaid exciting "electrical reaction thereof;

3. A multi-step selective amplifying apparatus comprising several units connected in cascade, each of said units including a circuit containing a high resistance conductor, asou'rce of electric energy, a vacuumn tube exited by an electrical reaction of said circuit, and a negative resistance-compensator for lmpressxng upon said circuit a nega- .tive resistance reaction whose energy lis de-v rived from said source and of a frequency determined by the pulsating electromotive fore fof said tube.

4. A multi-step selective amplifying apa minimum at the critical frequency, andi paratus comprising several units connected lin cascade, each of said units including a high resistance conductor, a vacuum tube excited by the resistance reaction ofsaid conductor, a source of electric energy, and a negative resistance compensator arranged to transfer from said source to the circuit of said conductor electric wave energy under the control of the pulsating electromotive force of said tube.

5. A multi-step selective amplifying apparatus comprising several units connected in cascade, each of said units including a circuit of high dissipative impedance, a `vacuum tube excited by an electrical reaction of said circuit, and a wave balance having secondary circuits in inverse series connection and arranged to be energized by the pulsating Vfelectromotive force of said tube for the purpose of impressing upon said circuit a negative resistance reaction of the frequency of the electromotive force to be amplified.

6. A multi-step selective amplifying apparatus comprising several units connected in cascade, each of said units/including a circuit of high dissipative impedance, a vacuum tube excited by an electrical'reaction of said circuit, a source ofelectric energy, and a Wave balance arranged to transfer by inductionfrom said source'to said circuit electric wave energy under the control of the pulsating electromotive force of said tube.

7. A multi-step selective amplifying apparatus comprising several units connected in cascade, each o f said units including a circuit containing a high resistance conductor, a control device excited by an electrical reaction of said circuit, a source of electric energy, a wave conductor arranged to be energized by a pulsating electromotive force whose energy is derived from said source and whose frequency is determined byAv said device, and means inductively associated with said wave conductor andarranged to impress upon said circuit a negative resistance reaction designed to diminish the losses-f1 paratus comprising several units, each of said units including a circuit of high dissipative impedance, a control device excited b v an electrical reaction ofv said circuit, a source of electric energy, a negative reslstance compensator controlled by said device and which by conveying power from said source to said circuit increases said excitingpensator arranged to transfer from said source t0 said circuit electric wave energy under the control of the pulsating electromotive force of said tube, and a pilot conductor having a vacuum tube associated therewith for connecting said units in cascade.

10.A multi-step selective amplifying apparatus comprising several units connected in cascade, alternate units of said apparatus including a circuit of high dissipative iinpedance, a vacuum tube excited by an electrical reaction of said circuit, a source of electric energy, a negative resistance compensator controlled by said tube and which by conveying power from said source to said circuit increases said exciting electrical reaction, the other units of said apparatus including a pilot conductor having capacity and resistance, and' a vacuum tube associated with said pilot conductor.

l1. A multi-'step selective amplifying apparatus comprising several units, each of said units including- (1) a resistance leach-(2) a vacuum tube excited by the re.- `sistance reaction of said load-(3) a source of electric energy,-and (4) a wave balance having secondary coils in inverse series connection and arranged to transfer from said Source to the circuit of said load electric Wave energy under the control of the pulsating electromotive force of said tube for the purpose of increasing .the selectivity of the circuit of said load and for thereby increasing the resistance reaction of the load, and a pilot conductor and vacuum tube associated therewith for connecting said units in cascade.

l2. A selective amplifying apparatus comprising a circuit of high dissipative impedance, a control device excited by an electrical reaction of said fcircuit, and means,

controlled by said device for impressing on said circuit a negative resistance react-ion suliciently large to compensate to any desirable limit the losses due to the high dissipative impedance of said circuit.I all oscillatory circuits of said apparatus in which the occurrence of disturbing oscillations affects the selectivity of the apparatus being substantially aperiodic.

13. A selective amplifying apparatus comprising a circuit of high dissipative impedance, a control device excited by an elec trical reaction of said circuit, ya source of l electric energy,` and a negative resistance compensator controlled by said device for transferring electric wave energy from said source to saidcircuit, all oscillatory circuits of said apparatus in which the occurrence of disturbing oscillations affects the selectivity of the apparatus being substantially aperiodic. i 'L 14. A selective amplifying apparatus comprising a circuit of high dissipative imlOO pedance, a vacuum tube excited by an electrical reaction of said circuit, a source of electric energy, and a negative resist-ance compensator arranged to transfer from said source tosaid circuit electric Wave energy.

under the control of the pulsating electromotive force of said tube. all oscillatory circuits of said apparatus in which the occurrence of disturbing oscillations affects the selectivity ofthe apparatus being substantially aperiodic.

15. A selective amplifying apparatus comprising a circuit of large resistance, a

control device excited by an electrical reaction of said circuit, a source of-electric energy,a wave conductor arranged to be energized bya pulsating electromotiveforce Whose energy is derived from said source and Whose frequency is determined by said device, and secondary coilsinductively associated with said Wave conductor and arranged to-impress upon said circuit a negative resistance reaction designed to diminish the losses due to the high resistance of said circuit.

16. A selective amplifying apparatus comprising a-eircuit high resistance, a vacuum tube excited by n electrical reaction of said' circuit, a source of electric energy, a Wave conductor arranged to be energized by a pulsating electromotive force Whose energy is derived from said source and of a frequency determined by the pulsating electromotive force of said tube, and means inductively associated with said Wave conductor and arranged to impress upon said circuit a negative resistance reaction designed to diminsh the losses due 'to the high resistance-of said circuit.

17. A selective amplifying -apparatus comprising a circuit of large dissipative im.

pedance, a control device excited by an electrical reaction of said circuit, a source of electric energy, and a Wave balance arranged to transfer by induction and under the con- 19. In an apparatus of the character de.

scribed, an electric circuit, a source of electric energy, and a Wave balance having a Wave conductor and secondary coilsfin inverse series connectionv for impressing on said circuit a negative resistance reaction. whose energy is derived from said source.

J20. 'in an apparatus of the character described, a scarce cf alternating electromotive force, an electric circuityconnected to said source,an independent source of electric energy, and a Wave balance having a wave conductor energized by a pulsating electromotive force Whose frequency is determined by the frequency of said alternating'electromotive force and whose energy is derived from said independent source and having secondary coilsin inverse series connection for impressing on said circuit a negative resistance reaction. 21. In an apparatus of the character, described, a source -of alternating electromotive force, an electric circuit connected to said source and having large dissipative im-i'` pedance, an independent source of electric energy, and means for rendering the im'- pedance of said circuit selective with respect to the frequency of said alternating source and including a Wave balance having a wave conductor energized by a pulsating electromotive force whose frequency is determined by the frequency of said alternating source and Whose energy is derived from said independent source.

22i In an apparatus of the character described, a source of alternating eiectromo- `tive force, an electric circuit connected to `said source and having large dissipative impedance, a vacuum tube excited by an electrical reaction of said circuit, and means for rendering the impedance of said circuit selective with respect to the frequency of said alternating source and for increasing said exciting electrical reaction, said means including a Wave balance having a Wave conductor controlled by the pulsating electro- .motive force of said tube and arranged to transfer by induction electric Wave energy from said source to said circuit.

23. 1n an apparatus of the character described, a circuit having large dissipative im' pedance, afsource of electric energy, and a Wave balance having a 'Wave conductor energized by a pulsating electromotive force of a predetermined frequency and having secondary coils in inverse 'series eonnec associated with said circuit and which 1- conveying power 'thereto from said source renders the circuit selective With respect to.` alternating electromotive forces of said predetermined frequency.

24. A selective amplifying apparatus, comprising a source of electromotive force to be amplified, a highresistance conductor` connected in series relation with said sourcelu a vacuum tube amplifier excited .by the re .Y sistance reaction fof said conductor, land' meansA electrically associated with said conductor for impressingon thecireuit thereof a negative resistance' reaction designed to increase the resistance reactionv of said conductor and hence the excitation of said am- "plifieiz 25. A, selective amplifying "apparatus comprising a source of electromotive force to be amplified, a high resistance conductor connected in series relation With said source, a vacuum tube amplifier having its grid excited by the voltage drop of said conductor, a local source of electric energy for said amplifier, and means electrically connected to said conductor for impressing on the circuit thereof an electromotive force of the same frequency as the electromontive force to be amplified and Whose energy is derived from said local source.

26. A fselective amplifying apparatus, comprising a Wave balance having a Wave conductor and two secondary coils inductively associated therewith and spaced apart substantially one-half Wave length with respect to the frequency of the electromotive force to be amplified, a high resistance conductor connected in series relation With said coils, a device for amplifying alternating electromotive forces arranged to be excited by the resistance reaction of said high resistance conductor, a local source of electric energy, and means for impressing on said Wave conductor an electromotive forceof the same frequency as the electromotive force' to be amplified and Whose energy is derived from said local source.

27. A selective amplifying apparatus, comprising a source of electromotive force to be amplified, a high resistanceconductor connected in series relation with said source, a vacuum tube having a grid excited by the resistance reaction of said conductor, a Wave balance having a Wave conductor and two secondary circuits inductively associated therewith and included in series relation in the circuit of said high resistance conductor, said secondary circuits being so arranged and connected that the electromotive forces induced therein of the frequency of the electromotive force to be amplified are of the same time phase and actin conjunction, a source of electric energy, and means for impressing on said Wave conductor an electromotive force of the same frequency as the electromotive force to be amplified and Whose energy is derived from said source.

In testimony whereof I afiix my signature.l

menant invonsKY Burnt. 

